The post of Führer der U-Boote (FdU) ("Leader of the U-boats") was the senior commanding officer of the submarine service in the pre-World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 German Kriegsmarine

Kriegsmarine

The Kriegsmarine was the name of the German Navy during the Nazi regime . It superseded the Kaiserliche Marine of World War I and the post-war Reichsmarine. The Kriegsmarine was one of three official branches of the Wehrmacht, the unified armed forces of Nazi Germany.The Kriegsmarine grew rapidly...

, and the title of several senior commands during the war. From January 1936 and until 17 October 1939, Karl Dönitz

Karl Dönitz

Karl Dönitz was a German naval commander during World War II. He started his career in the German Navy during World War I. In 1918, while he was in command of , the submarine was sunk by British forces and Dönitz was taken prisoner...

 served in this position. Thereupon Dönitz was named Befehlshaber der U-Boote (BdU) ("Commander of the U-boats"), and two subordinate FdU posts were established, FdU West ("FdU West") and FdU Ost ("FdU East").

In the further course of the war, several further posts were created:

• F.d.U. Ausb. - Führer der U-Ausbildungsflottillen: Head of the training flotillas
• F.d.U. Italien - Führer der U-Boote Italien: Head of the U-boats for Italy
• F.d.U. Mitte - Führer der U-Boote Mitte: Head of the U-boats for the central sector
• F.d.U. Mittelmeer - Führer der U-Boote Mittelmeer: Head of the U-boats for the Mediterranean
• F.d.U. Nordmeer - Führer der U-Boote Nordmeer: Head of the U-boats for the North Sea
  North Sea
  In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...
  
  
• F.d.U. Norwegen - Führer der U-Boote Norwegen: Head of the U-boats for Norway
• F.d.U. Ost - Führer der U-Boote Ostsee: Head of the U-boats for the Baltic Sea
  Baltic Sea
  The Baltic Sea is a brackish mediterranean sea located in Northern Europe, from 53°N to 66°N latitude and from 20°E to 26°E longitude. It is bounded by the Scandinavian Peninsula, the mainland of Europe, and the Danish islands. It drains into the Kattegat by way of the Øresund, the Great Belt and...
  
  
• F.d.U. West - Führer der U-Boote im Westraum: Head of the U-boats for the West (France)